Yanmar 4BY, Service Manual, Page: 121 / 275

ENGINE
5-66
BY Service Manual
Cylinder Block and Crankshaft
Inspection of Cylinder Block
1. Remove all main bearing inserts. Ensure the
bearing seating surfaces are free of any debris.
2. Ensure that oil passages are clear and
unobstructed.
3. Check for discoloration or evidence of cracks. If
a fracture is suspected, use the color check
method or the MAGNAFLUX method to
determine if the cylinder block is fractured.
Figure 5-111
4. Measure cylinders for roundness, taper and
inspect for evidence of scoring. Consider
honing or replacing the cylinder block if the
measurements are not within specification.
5. Take measurements at three places (a, b, c) ,
and in two directions (d and e) in each cylinder.
Cylinder Bore Specifications
Crankshaft Installation
1. Select the correct bearing as follows:
Figure 5-112
(a) Locate and record the grinding size of
crankshaft (Figure 5-112) .
Figure 5-113
(b) The crankshaft will be marked with yellow,
green or white paint to determine the correct
bearing shell to install in the bearing caps
(Figure 5-113) .
Inspection Item*
*Values are for new or reconditioned cylinders.
Specification
Bore Diameter stage 0 84.007 ±0.007 mm
Bore Diameter stage 1 84.257 ±0.007 mm
Permitted out of round of cylinder
bore
0.005 mm
Permitted conicity of cylinder
bore
0.01 mm
00002 3 0B
a
b
c
d
e
20 mm
(0.75 in.)
20 mm
(0.75 in.)